How to use own types instead of scala standard types in sbt?

Question

I have the following for learning.

package learning.laziness

sealed trait Stream[+A] {
  def headOption: Option[A] = this match {
    case Empty => None
    case Cons(h, _) => Some(h())
  }

  def toList: List[A] = this match {
    case Empty => List.empty
    case Cons(h,t) => h()::t().toList
  }
}
case object Empty extends Stream[Nothing]
case class Cons[A](head: () => A, tail: () => Stream[A]) extends Stream[A]

object Stream {
  def cons[A](hd: => A, tl: => Stream[A]): Stream[A] = {
    lazy val head = hd
    lazy val tail = tl
    Cons(() => head, () => tail)
  }
  def empty[A]: Stream[A] = Empty
  def apply[A](as: A*): Stream[A] =
    if (as.isEmpty) empty else cons(as.head, apply(as.tail: _*))
}

When I load the REPL via sbt console and enter for example

• Stream(1,2)
  • res0: scala.collection.immutable.Stream[Int] = Stream(1, ?)
• Stream.apply(1,2)
  • res1: scala.collection.immutable.Stream[Int] = Stream(1, ?)
• Stream.cons(1, Stream.cons(2, Stream.empty))
  • res2: Stream.Cons[Int] = Stream(1, ?)

It uses Stream from scala.collection.immutable in the two first cases instead of mine. How can I make sbt only use mine?

Answer 1

In the SBT console, import your class before attempting to use it:

scala> import learning.laziness.Stream
scala> Stream(1, 2)
scala> //etc.

Your Stream class's code must be under an SBT source folder (by default, this would be src/main/scala, relative to the project root directory, or in a custom source directory specified by an SBT scalaSource in Compile directive - it will not be found and compiled by SBT otherwise). As the code you provide is in the package learning.laziness, then the default location for your Stream.scala source file would need to be src/main/scala/learning/laziness. Once SBT knows where to find your file, you should then be fine.